Composition and method for producing combination corrosion resistant and lubricatingcoatings on metals



COMPOSITION AND METHOD FOR PRODUCING COMBINATION CORROSION RESISTANT AND LUBRICATING COATINGS ON METALS Earl Eugene Logue, Jr., Birmingham, and Ernest P. Bell,

Detroit, Mich., assignors to Parker Rust Proof Company, Detroit, Mich, a corporation of Michigan No Drawing. Application June 8, 1953 Serial No. 360,353

Claims. (Cl. 148-615) This invention relates to a composition and method for producing a coating on metallic surfaces and particularly ferrous surfaces which functions both as a corrosion-resistant coating and as a lubricant in operations deformation is relatively severe. The harder metals such as iron, steel, stainless steel and the extremely hard alloy steels have been successfully deformed by preliminarily coating the metal surface with an underlayer of a protective chemical coating suchas a phosphate, oxide, 'sulfide or oxalate together with an overlayer of a conventional lubricant. .Such conventional lubricants have ineluded ordinary lubricating oils; extreme pressure lubrieating oils; fats or soaps in aqueous and .dry form; and fats, oils, or soaps in combination with a variety of infusible pigments such as clay, graphite, mica, etc. In employing the combination of a chemical coating and a lubricant, it has been necessary heretofore to employ separate compositions and sequential steps of first treating the metal with a phosphate solution, then a first rinse in water and a second rinse in water or a slightly akaline solution, and thereafter treating the phosphate coated article in a suitable lubricant composition.

It is the principal object of this invention to provide a single composition which produces on a metallic surface a coating which is both protective and has lubricating properties enabling relatively severe deformation of harder metals such as iron and steel.

Another object is to provide a method, for forming on a metallic surface an integral chemical coating which has lubricating properties.

A further object'is to provide an inexpensive composition and a simple one-step method, which eliminates the necessity for using the customary two-stage rinsing, for producing an integral chemical coating having lubricating properties on metallic'surfaces, and particularly ferrous surfaces. A still further object is to provide an aliphatic phosphate coating on metal surfaces which has lubricating properties. .Other objects and advantages. of the invention will appear .in'the following detailed description of the invention. v

These and related objects are accomplished in accordance with this invention by coating the surfaces of metals, particularly ferrous metals, by contacting the surface with an aqueous dispersion or admixture containing as, the essential coating producing ingredients an aliphatic ester of phosphoric 'acidvhaving from 8-18 carbon atoms, and

a" metallic ion that forms a salt with the aliphatic ester of phosphoric acid which is compatible with the dispersion, said dispersion or admixture having a controlled acidity within a rangeof pH- of about 3.0 and 5.5. By

compatible with the dispersion is meant that the metal lic salt of the aliphatic phosphate is soluble in or at least semi-soluble or readily dispersible in the aqueous solution or dispersionof the aliphatic ester; The "coating which is formed by this treatment has a velvety appear ance and is-an amorphous type of coating, being partially greasy and capable of being crushed to a continuous unctuous film so that it is well suited for use as a'lubricant in metal deformation operations. The coating is excep tionally adherent and-resists removal from thefsurface of the metal even when the highest pressures normally encountered in deformation operations are used.- In addition to the aliphatic phosphoric acid ester andthe metallic salt thereof, the composition may also contain an amine which is reactive'with a portion of the aliphatic phosphoric "acid ester to form' a compatible-amine salt' thereof and an oxidizing or accelerating agent which isunderstood that the incorporation of an amine which forms a compatible amine salt with the aliphatic phosphoric ester is but one means of achieving the desired degree of acidity and that the benefits of the invention may be obtained in 'the absence of either or'both the amine and the accelerating agent. It i's'to be'fu'rther understood, however, that the incorporation of an amine in the basic composition produces a preferred composition for reasons which will be explained in greater detail hereinafter, and that the best solutions of this invention also include an accelerating agent or agents: I

The aliphatic esters of phosphoric acid which, in coins bination with a metallic salt of such ester, have been found to be useful for the purposes of this invention, are, the esters-which may be regarded as the reaction products of phosphoric acid with aliphatic alcohols containing from 818 carbon atoms. The aliphatic portion ofthe ester may be either saturated or unsaturated. While the saturated alcohols are somewhat more readily commer cially available, the unsaturated aliphatic esters having unsaturation of the olefinic type havenevertheless been found to be equally suitable in the compositions of this; invention. When the length of the carbon chain in the ester is lessthan 8 carbon atoms, the coating which is produced does notexhibit the characteristics of a .lubri-. cant to a desirable degree, and when the length of the carbon chain exceeds about 18 carbon atoms, the. aliphatic phosphate ester is insufficiently dispersible in waterJto form a workable material; Preferred materials for the, purposes of this invention are the lauryl esters and the oleyl esters. Mixtures of esters having carbon chain lengths between 8 and 18 may beused, and mixtures of esters actually represent a preferred form of the invention because alcohols of mixed carbon chain length are readily available andthe mixed esters are easily obtained. Pro-' portions of esters which have been found to be suitable are in the range of about 3 grams/liter to about 201 the aliphatic phosphoric acidester, a salt which is soluble, .or at least semi-soluble or readily dispersible in, the;

aqueous'dispersion'of the aliphatic phosphoric acid ester.

Patented June, 24, 1Q58 a this in- Typicalmetallic ions which have been found to be useful rat this purpose ihcludeziii'c, aluminum, the alkali'metals including ammonium, cadmium, copper, nickel and iron.

t s P e o rqbtainn s e m from n aqueousdispersion containingpnly an aliphatic; phosphoric acid. esterhaving 8l8 carbon atoms,.the film soproduced is; ofinferior. quality, has poor adhesion and appears to be an adsorbed filmrather than an integral chemical coating.

' The of acompatiblemetallic ion in the compositions of this invention apparently. imparts to the aqueous dispersion of aliphatic phosphoricacid ester, the

ability to chemically react with the surface and to form phosphoric acidiester having it -ls carbonatoms and a.

compatiblemetal ion are. sufliciently adherent and possassedr of a greasy'nature 1such thatjupon the application of. pressure; the velvety,, amorphous coating is crushed intoacontinuous film. having, goodlubricating. properties. andlhigh resistanceto being, dislodged due to the applicationoftpressurea M TlZheproportion of metallic ion whichis necessary for the formation of theisuperior coatings of this invention is relatively restricted. In the operating solutions, the metallicion content-may,satisfactorily vary between about 0.3" gram per liter and 11.0 grams per liter of zinc or the equivalent proportion of other suitable metallic ion, such astthose enumerated hereinabove. When the metallic. ion contentdropsbelow the equivalent of 0.3 gram/liter of zinc, the coatingis a relatively non-adherent greasy film, Whereas when the concentration ofmetallic ion exceeds the-equivalent of 11 grams. per, literof zinc, the salt of thy ester cannot be maintained in dispersion and precipitation occurs. i

metallic ion is preferably introduced into the composition as a salt and only limited quantities may be introduced as, basic-salts or hydroxides. When a relatively high tconcentration of. metallic ion is desired, introduction; of: the metallic ion as a basic? salt or a hydroxide is notfeasiblesince the pH islraised above the operable limit-before the desired concentration is achieved. In this case, metallic salts: such as the acetates or nitrates should be "employed; and: the .pH adjusted 1 with the amine being employed. The. use of. salts containing a halide, such as chloride, bromide or iodide-is not recommended.

Theincorporationof an amine in the basic composition of this-inventiontendstoincreasethe. solubility of the metallic salt of the aliphatic .phosphatein the dispersion. Foli the, purposeof. obtaining coatingswhich are relatively heavyand which. are especially suited for sever deformation. operations, it. is. desirable to: maintainthe concentration of the metallic salt: near the maximumdegree of its. solubility. The. presence of an. amine additionally raises 3-isopropoxyrpropylamine, triethanol. amine and morpholine. Theproportion of amine which may be used is that; amount which produces the desired pH within the range of 3'.0'-5'.5. p

lhenumerical'pH limits of 3.0" to 5.5 refer to a pH determined with Hydrion papers. Ithas been found that although the absolute degree of precision generally obtainable with Hydrionpapers is less than. that of glass electrodes, the reproducibility and accuracy of: the

'4'- determinations with Hydrion papers for the dispersions of this invention are actually better than those obtainable using glass electrodes.

The compositions of this invention from the desired coatings in a shorter period oftime when they include an accelerating or oxidizing agent. Any oxidizing agent whichis conventionally employed for the purpose of accelerating the formation of a coating from a solution such as zinc phosphate or manganese phosphate solution, may be used for the purposes of this invention. Typically useful oxidizing agents include the nitrites, nitrates, peroxides; chlorates, bromates, sulfites and nitro-organic compounds such as rn-nitrobenzene sulfonate and picric acid. For convenience, the oxidizing agents may be added as the metallic salts such as the sodium or other alkali metal salt, and the proportion of metallic ion so introduced is small and relatively insignificant to the overall metallic ion content. Suitable concentrations of these oxidizing agents whichmay be employed to decrease the time required for' producing the coatings of this invention are 0L3%'O15'% sodiummeta nitro benzene sulfonate; 0i0l%-0.5 picric acid}, ODS-0.3% hydrogen nitrate; O.Ol%--0.3'%' hydroxylamine.

Broadly stated, the method of this invention comprises the steps of contacting the metal surface to be treated with the compositions ofthis invention and thereafter drying the coating thus formed on the metallic surface. As is usual with phosphate coating solutions, it is desirable to apply the compositions of this invention while hot and to regulate the time of solution contact with the metal surface and the concentration ofthe solution so as to produce the desired thickness of coating. Temperatures between about F. and 190F. may be employed. The step of drying, the coating on the metal surface is preferably performed at an elevated temperature less than about 250 F., though where the time required for fully preparing the metal surface to be drawn is unimportant, the coating may be dried in air. Where the coating is dried by subjecting the same to an elevated temperature, a somewhat. increaseddegree of reaction with the metal surface is thought to occur and the resultant coating is somewhat improved in its adherence to'the metal surface. Drying the coatingat an elevated temperature represents the preferred procedure.

The examples given below illustrate in greater detail typical'compositions of, and themethod of this invention.

EXAMPLE I A mixturewas prepared by heating together 26.5 grams of monolauryl phosphoric acid and 4 grams of zinc, oxide with 500 ml. of water and mixing in a Waring blender. The resultant'mixture had a'pHof 1.2 which was adjusted with sodium carbonate to 55. Clean,.mild steel panels were immersed in the: solution at F.- F. for periods of one-halfminute to two minutes, withdrawn 'and dried. All the panels were coated with a smooth,

adherent, water repellentcoating which was somewhat dusty in appearance. The coatings crushed to a thin unctuous film on the application of pressure.

Distilled water tomake 2: gallons.

The emulsion containing the above ingredients was.

stable and had a pH of 5.0. Three hundred and fifteen 4" x 6 steel" panels were processed through the solution at 140 F.'-1501"'F. for 5 minutes each. Smooth adherent coatingswere formed which were slightly more unctuous thanthe coatings of Example I.

A number of formulations were prepared corresponding to that set forth above in Example H except the morpholine was omitted, and in separate formulations .was re-' placed by a chemically equivalent proportion of. ammonia, triethanolamine, hydrazine, and 3-isopropoxypropylamine. Steel panels treatedin these modified solutions in the same manner were coated with coatings generally similar to those obtained when morpholine was present.

EXAMPLE HI A 100 gallon aqueous emulsion was prepared containing:

The pH of the solution was adjusted upwardly to 5.3 by adding 1 liter of concentrated ammonium hydroxide. A number-of pieces of steel tubing. were-immersed in the solution at 140 F.-150 F. for 5 minutes, withdrawn and force dried. The coatings were uniformly smooth and adherent.

Several pieces of /2 inch outside diameter steel tubing having a wall thickness of 0.015" were so coated and drawn to 0.400" outside diameter x 0.014" wall thickness, and immediately redrawn to 0.345" outside diameter x 0.0115" wall thickness for a total reduction of 47%. The temperature of the tubing during drawing remained low and the surface of the drawn tubing was good.

The chemicals in the emulsion are depleted as the emulsion is used for coating, and may be easily replenished by the use of a replenishing concentrate. Suitable formulations for replenishing or for original make-up are given below:

This concentrate is in the form of a heavy paste and is best compounded by heating the acids to melting and adding the morpholine thereto at about 200 F. and maintaining the temperature until the reaction is complete. The sodium hydroxide may be dissolved in part of the water and the acetate and nitrate in the balance and both solutions heated to about 150 F. While the caustic is being stirred, the mixture of acids with morpholine and the acetate-nitrate solution are added slowly and after about 15 minutes of mixing a uniformly blended heavy paste is obtained. A working solution may be prepared by using about'60 to 70 pounds of this concentrate per 100 gallons of solution or emulsion, and adding an oxidizing agent thereto.

NaQH 1 Distilled water to make 250 ml.

This formulation when mixed as described above in Formula I, produced a heavy, creamy material.

What is claimed is:

1. A composition of matter comprising an aqueous dispersion consisting essentially of water, a mono-aliphatic phosphoric acid ester having from 8 to 18 carbon atoms,

a metal ionwhich formsa-salt with the said phosphate and which is compatible with said dispersion in an amount f equivalent to about 03-11 grams/liter of zinc, andan amine in an amount sufficient to produce a pH between about 3.0 and 5.5.

' 2. A composition of matter comprising an aqueous dispersion consisting essentially of water, a mono-aliphatic phosphate having from 8 to 18' carbon atoms, a metallic ion'in an amount equivalent to about 03-11 grams/liter of zinc, an oxidizing agent and an amine in an amount sufficient to produce a pH between about 3.0 and 5.5.

3. A composition'of matter comprising an aqueous'dispersion consisting essentially of water, a monoaliphatic phopshate having from 8 to 18 carbon atoms in an amount from about 3 to grams per liter, a metallicion which yields with said phosphate a salt which is at 4. The method of forming on a metallic surfaceanintegrally bonded chemical coating having lubricating properties which comprises the steps of contacting the metal surface with an aqueous dispersion consisting essentially of water, an aliphatic phosphate having 8 to 18 carbon atoms and a metal ion which'yields a salt which isvat least semi-soluble in said dispersion in an amount equivalent to about 0.3-11 grams/liter of zinc and having a pH of about 3.0 to 5.5, and thereafter drying the said coating at an elevated temperature.

5. The method of forming on the surface of a ferrous article an integrally bonded chemical coating having lubricating properties which comprises the steps of immersing the article in an aqueous dispersion at a temperature between about F. and F. for a short time, which dispersion consists essentially of water, a monoaliphatic phosphate having 8 to 18 carbon atoms in an amount of about 3 to 80 grams per liter and a metallic ion which yields with said phosphate a salt which is at least semi-soluble in said dispersion in an amount equivalent to about 0.3 to 11 grams per liter of zinc, said dispersion having a pH between about 3 and 5.5, and thereafter drying said coating at an elevated temperature less than about 250 F.

6. The method of forming on the surface of a ferrous article an integrally bonded chemical coating having lubricating properties which comprises the steps of immersing the article in an aqueous dispersion at a temperature between about 90 F. and 190 F. for a short time, said dispersion consisting essentially of water, a monoaliphatic phosphate having from 8-18 carbon atoms and a metallic ion which yields with said phosphate a salt which isat least semi-soluble in said dispersion in an amount equivalent to about 0.3-11 grams/liter of zinc, an oxidizing agent and an amine, said dispersion having a pH between about 3.0 and 5.5, withdrawing the article, and drying the coating thereon.

7. The method of forming on the surface of a ferrous article an integrally bonded chemical coating having which is at least semi-soluble in said dispersion and which is present in an amount equivalent to about 0.3 to 11 grams/liter of zinc, an oxidizing agent, and an amine in an amount sufficient to produce a pH of between about 3.0 and 5.5.

8. A metallic surface having thereon a metallic aliphatic phosphate coating produced by the method claimed in claim 4.

9i A-con'centrate-for use inthecmake-upand replenish.- j v Grams ing-"ofiaqueousemulsions suitable for' forming integral: Ferric nitmte19H 0 6 chemical ooatings on metallic surfceshaving lubricating NaoH: 2". 1 propertieswhich consists essentially of: Distilled waterm make' 2ifl ml1 512;? L2Fpfi?!?::::;::::133:::fiif: 323' Mum Cited-9191191119 ofi 19PM Stearyl aci'dphospha.te do 790 I T E AT N Mbrpholine 1,900,973 Bertsch Mar. 14, 1933 Sodihm hydroxide; 5w, 1,936,534 Albrecht; ,1 Nov. 21, 1933 Sbdium' acetate-31120 2,080,299 Benning et a1. May 11, 1937 s fl nitrate-9Hz0 188 2,2853853- Downingetal'. June- 9, 1942 DistilledTwater 4 2,328,540 Hochwalt Sept. 7, 1943 1 110. A concentrate for use in the make-up and replenish- 234323784 M111 at 1947 ingfioftaqucouswemuisionssuitable for forming: integral 15a 2,452321' et'all C, chemicalicoatings on. metallic surfaceshaving; lubricating 27456347 lfmstedt 4 Dem 1948 properties whichxconsistsiessentially of: 2,574,955" Blshop 3 1 l 1 m 2';739;9'15-' Schustereral Mar; 27, 1956 Monol'aunyl acid phosphate 15' r Monoeoleyli acid phosphate; 1 7 20 FOREIGN PATENTS 782,286 Great Britain June 2 2, 1955 Morpholine 7 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 2,840,498 June 24,- 1958 Earl Eugene Logue, Jr et al It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, ,line 62, for "20" read ee 80 -r=-=;-; column 3, line 51., for "Sever" read ==e'=- severe s; column 4;, line 4., for "from" read form em.

Signed and sealed this llth day of November 1958,

(SEAL) Attest:

KARL H .mmr Attesting Ofiicer 7 ROBERT C. WATSON Commissioner of Patents 

1. A COMPOSITION OF MATTER COMPRISING AN AQUEOUS DISPERSION CONSISTING ESSENTIALLY OF WATER, A MONO-ALIPHATIC PHOSPHORIC ACID ESTER HAVING FROM 8 TO 18 CARBON ATOMS, A METAL ION WHICH FORM A SALT WITH THE SAID PHOSPHATE AND WHICH IS COMPATIBLE WITH SAID DISPERSION IN AN AMOUNT EQUIVALENT TO ABOUT 0.3-11 GRAMS/LITER OF ZINC, AND AN AMINE IN AN AMOUNT SUFFICIENT TO PRODUCE A PH BETWEEN ABOUT 3.0 AND 5.5. 